Workability, strength and microstructural properties of ground ferronickel slag blended fly ash geopolymer mortar

This study evaluated the effect of using ground ferronickel slag (GFNS) with fly ash (FA) to produce geopolymer mortar. Workability of mortar was found to decrease with the increase of GFNS content due to its angular shape. Compressive strength was found to maximize at GFNS content of 75%. The 28-day and 90-day compressive strengths of geopolymer mortar using 40% alkaline liquid were 75 and 96 MPa, respectively. The SEM images showed more compact microstructure of geopolymers using GFNS compared to that using 100% fly ash. The quantitative XRD results confirmed the production of amorphous geopolymer product. The energy dispersive X-ray spectra (EDS) revealed that the main reaction product of FA-GFNS geopolymer is sodium magnesium alumino-silicate hydrate (N-M-Al-Si-H) gel, which is provided the denser microstructure and the resulting strength increase by GFNS. The porosity and sorptivity of the mortar were found to decrease with the increase of GFNS.